Smokeless powder



' SMOKELESS roan.

' Elton n. n, Wharton, N. a, gnor to Hercules ll'owder Company, W

ilmington, Dei a corporation oi Delaware No Drawing. ApplicationNovember c, 1940, Serial No. cameo 4 Claims.

This invention relates to a method of preparing progressive burningsmokeless powder and more particularly to an improved method of coatingsmokeless powder with a deterrent material, and to smokeless powdercoated with a water soluble deterrent material.

It has been known to coat smokeless powder with a deterrent material inorder to provide for a close control of the burning rate and to producea high velocity of the projectile without excessively high breechpressures. Such coating materials desirably penetrate the powder grainsmore or less, so that as the powder burns, the successively exposedsurfaces contain grad- 'ually less and less of the deterrent material,thus causing the combustion of the grains to proceed with increasedspeed.

Treatment of smokeless powder grains with deterrent to render theircombustion progressive, by methods heretofore known, while producing thedesired results to a degree, has been open to a number of objections.For example, the use of a deterrent and powder grains alone requireslong continued heat and tumbling to obtaini uniform distribution ofdeterrent on thepowder grain which may lead to explosion. The use ofwater with the deterrent and powder grains requires long treatment andrenders uniform coating dimcult on account of the water insolubility ofmany deterrents heretofore known. The use of a deterrent solvent, e. g.,benzol, is open to the great risk of explosion of solvent vapors, theirpoisonous nature, and the economic necessity for recovery of thesolvent. The use of prior known water soluble deterrents has furthermorenot produced smokeless powder of high ballistic st bility, i. e., themaintenance with age of the al ballistics produced by the powder.

is an object of this invention to produce a coated smokeless powderwhich overcomes the disadvantages of prior known powders.

it is a further object of this invention to produce a smokeless powdercoated with a water soluble deterrent substance.

A. still further object of this invention is to produce a smokelesspowder coated with phthalide.

A further object of this invention is to producea coated smokelesspowder which has an improved hot storage ballistic stability.

Qther objects will appear hereinaiter.

The objects of my invention are accomplished by coating grains ofsmokeless powder with phthalide.

As an example for carrying out my invention 100 parts by weight ofdouble base (29% N. GJ)

riflle powder granulated .045.015 x 1/21 were placed in a sweetie ortumbling barrel and wet with 15 parts by weight of cold water. The wetpowder was tumbled and heated to 75, C. and then 5 parts by weight ofphthalide added. The mixture of powder, water and phthalide was agitated30 minutes at 75 C. and 30 minutes at 85 0., removed from the barrel,dried, glazed and humidified. One portion of the powder was stored for30 days at 50 C. and another portion for 30 days at normal atmospherictemperatures and then both portions rehumidified. The powder which hadbeen stored hot wasithen tested in direct comparison with the powderwhich had been stored at normal temperatures.- For the sam charge ofpowder the hot storage sample produced 1,000 lbs/sq. in. higher pressurethan the normal storage powder.

' parts by weight of double base (20% N. G.) rifle powder granulated.045.015 x 1/21 were placed in a sweetie barrel and wet with 15 parts byweight of cold water. The wet powder was 2 tumbled and heated to 75 C.and title parts by weight-oi diacetin added. The mixture of powder,water and diacetin was agitated minutes at C. and 30 minutes at 0.,removed from the barrel, dried, glazed, and humidified. One 30 portionof the powder was stored for 30 days at 50 C. and another portion for 30days at normal atmospheric pressures and then both portionsrehumidifled. The powder which had been stored hot was then tested indirect comparison 35 with the powder which had been stored at normaltemperatures. Fdr the same, charge of powder the hot storage sampleproduced 9,100 lira/sq. in. higher pressure than the normal storagepowder. I The increased hot storage capacity of smokeless powder treatedwith water soluble phthalide as compared to the water soluble diacetinis apparent from the above examples. I am not at present prepared togive a sound theoretical explanation of the improved behavior of powdercoated with phthalide as compared to powder coated. with previouslyknown water soluble deflig listic stability test. lihthalide is a solidunder As a comparison with the above example,

these conditions. It is my belief that poor bai listic stability iscaused by mobility of deterrent molecules and that the molecules ofdeterrent substances which are in the liquid state under normalconditions will have greater mobility than those of materials which aresolids under the same conditions. When a deterrent is applied to asmokeless powder grain, it penetrates into the powder grain surfacesmore or less according to the temperature of application, the solvent orplasticizing power of the deterrent, and the state of aggregation of thedeterrent. After the powder is dried, glazed, humidified and cooled tonormal temperatures, this penetration due to deterrent mobility nearlyceases. It may continue at a very low rate at normal temperatures but ifthe powder is stored at somewhat higher temperatures the mobility andpenetration tend to increase. Under thes conditions the deterrent whichis normally in the solid state.

of aggregation will give improved ballistic stability.

It is tobe understood that single base as ,well as double base riflepowder may be treated in accordance with th 'teachings of thisinvention. The amount of phthalide added may be varied in accordancewith the granulation of the powder and the deterrent effect desired.While 5% by weight of the weight of powder being coated was asatisfactory amount in the'instance of the example given it is to beunderstood that I am rent action.

Where in this specification I refer to phthalide I meanthe inner esterof o-hydroxy-methylbenzoic acid obtained by the reduction of phthalicanhydride or. chloride with Zn and HCl and which has a melting point of73 C., and a boiling point of 290 C.

My invention provides an improved smokeless powder having an increasedhot storage ballistic stability, and one which is comparatively safely,economically and eillciently produced. This powder may be used in themanufacture of cartridge ammunition.

What I claim and desire to protect by Letters Patent is:

1. A smokeless powder comprising smokeless powder grains surface coatedwith phthalide.

2. A double base smokeless powder comprising smokeless powder grainssurface coated with phthalide.

3. A single base smokeless powder comprising smokeless'powder grainssurface coated with phthalide.

4. A smokeless powder comprising smokeless powder grains coated withphthalide in amount from about 1% to about 10% by weight of the powder.

ELTON R. ALLISON.

